The present invention relates to a novel delamination apparatus and method, and more particularly to apparatus and a method for delaminating a composite sheet structure comprising a plurality of selectively releasable superposed sheets.
There are a great many prior art references disclosing apparatus and methods for separating layers of laminating film units, for instance, for the purpose of rendering a developed image visible. Such apparatus and methods are commonly used in connection with socalled peel apart film units and may utilize a blade of some kind insertable between two predetermined layers or sheets of a film unit fixed to the periphery of a rotating drum. For example see U.S. Pat. No. 4,670,085.
In general, the prior art apparatus and methods may be characterized as providing a peeling action, for instance removal of one layer from another. Such apparatus and methods however would not be suited for providing delamination as understood in the context of the present invention. Delamination in the sense used herein, is to be understood as meaning a process of separating cover or support sheets from opposite surfaces of a vertically frangible layer each carrying different portions of the frangible layer with it as determined by the strength of an adhesive bond at any given point between the surfaces of the layer and the respective sheet. Vertical frangibility of the layer as used herein is intended to mean the ability of the layer to break in a direction normal to its surface but to exclude breaking of the layer between its surfaces.
A device and method for providing the delamination as set forth above is disclosed in U.S. patent application Ser. No. 07/616,796, filed Nov. 21, 1990 and has proved successful in achieving its various objectives.
However, it is an object of the present invention to provide an improved apparatus and method for delaminating a composite sheet structure which provides a significant improvement in the loading and tab breaking compared to the prior art.
A further object of the invention is to provide an improved apparatus and method for delaminating a composite sheet structure comprising a plurality of selectively releasable superposed sheets which increases reliability of tab breaking during initial peeling and is simple in operation.
Another object of the invention is to provide an apparatus and method for processing a thermal imaging film unit by separating two sheets enclosing between them a layer of an image forming substance, to remove predetermined portions from the layer thereby to form two complementary images.
And still a further object of the invention is to provide a novel delamination apparatus and method which makes possible a selective removal of portions of a frangible layer by sheets adhered to opposite surfaces of the layer.